The 2003 Presidential Commission Report on the Future of the USPS concluded that the Postal Service should continue to develop effective merging systems that optimize efficiency, e.g., maximize the number of mailpieces shipped with each mile traveled, while minimizing the labor content associated with mailpiece handling. With respect to the latter, all elements of the mail stream (letters, flats, periodicals, post cards, etc) should be sorted, merged, and/or sequenced at a centralized location with the expectation that no subsequent handling would be required at each of the local postal branch offices, i.e., other than the physical delivery to the recipient address.
Most postal services are actively exploring opportunities to reduce the overall cost of processing mail by investing in postal automation equipment and employing state-of-the-art materials management techniques to improve efficiencies in various process steps. In some instances, the savings from automation equipment is, unfortunately, offset by increases in transportation costs. As will be explained in subsequent paragraphs, the costs/inefficiencies in connection with transportation are most clearly evident when investments are considered/made in automated sorting equipment associated with “flats” type mailpieces.
Sorting equipment adapted to handle flats type mailpieces typically employ a gravity feed chute for dropping mailpieces vertically into mail trays arranged below the chute. Occasionally, portions of the mailpieces do not settle properly and partially protrude/extend above the top of the tray. When the filled tray is transported using automated processing equipment, the potential exists for a protruding mailpiece to catch on various mechanisms/components of the automated equipment, e.g., one of the tray transporting, storing, and/or retrieving systems. It will, therefore, be appreciated that such interference can damage the mailpiece or, alternatively, require the system to shut-down to rectify the problem/obstruction. Further, the overall efficiency of the mail sortation system is adversely affected by such stacking errors.
Stacking errors can occur as a result of a variety of non-optimum conditions and/or under a variety of other circumstances. A principle cause, however, may be attributable to a non-uniform thickness profile of at least one of the flats envelopes in the mailpiece container. That is, flats-type envelopes are, due to their relatively large containment pocket, well-suited to mail/deliver irregular-shape objects such as medication/pill containers, record/music discs, articles of clothing, and other lightweight consumer products. As such, these flats mailpieces often exhibit an irregular thickness profile which can disrupt the ability of the mailpiece container to effect an orderly and/or level stacking of mailpiece items therein. For example, when mailpieces having inconsistent thickness are stacked using the drop-chute configuration described above, the stack in the mailpiece container/tray can become thicker on one side of the tray than the other. As such, this can lead to a greater frequency of mailpieces protruding beyond or above the top rim of the tray.
To address the difficulties associated with stacking errors, mailpiece sorting equipment manufacturers have typically employed one of two known methods/solutions. Firstly, the tray capacity may be limited to about 70% of the total capacity. As such, the probability that a mailpiece will protrude beyond the limits/bounds of the container is significantly diminished. Many of the current sorters are equipped with sensors to determine when the height of the mailpiece stack reaches seventy percent (70%) full level. Secondly, sensors may be deployed throughout the tray transport system to detect when or if mailpieces protrude beyond the top of the container/tray. Trays which have been over-filled are typically diverted to a secondary track for an operator to manually adjust the stacking error and return the tray to the primary or principle track.
While these solutions eliminate difficulties associated with equipment jamming or malfunction, the mailpiece container trays are not filled to their full capacity. As a result, the containers are shipped with thirty percent (30%) of its volume as air rather than in mailpiece content. Additionally, the labor cost in operating multi-million dollar sorting equipment remains high due to the human intervention required to correct for stacking errors.
A need therefore exists for a method and system to accommodate mail of inconsistent thickness, reduce stacking errors, and optimally fill the mail containers/trays.
The invention will be fully understood when reference is made to the following detailed description taken in conjunction with the accompanying drawings.